Help me design my hop schedule?

Greetings everyone, been a while since I've beer here!
Going for a nice summer American IPA. 5.5 gallon, US-05.

7lbs light DME, most of it at flame-out
6oz Crystal 60L
maybe a pinch (4oz) of dextrose, although I don't know if I need it. I've never used Morebeer.com's DME before so don't know how it compares to Munton's that I've always used. With the munton's I found a touch of sugar was necessary to dry it out a little for an IPA.

Anyway, here's what I've got for hops:
2oz Amarillo 8.2%
2oz Centennial 9.2%
2oz Citra 13.5%
2oz Columbus 13.9% as needed for bittering

Like for it to be around 70 IBU's with a decent dry-hop (no more than 2.5oz) and some good late hopping, as well as a flame-out addition. I could pick up some Cascade if that's not enough late hops, but that's all I can get local.

I used to use Hopville's software but since they "upgraded" it just seems to suck for calculating IBU's when you're doing extract. Plus I've never used Citra or Amarillo before so I though I'd see what you all thought was the best way to combine these hops. I'd like some Citra in the dry-hop but that's about all I know.

Thanks for any input!

I'm interested in this as well as I was planning an ipa with similar hops an was wondering how to do a hop schedule that would best blend the flavors and aromas.

Well, here's what I went with:

40 min - 1oz columbus

15 min - 1/2oz amarillo
15 min - 1/2oz centennial

10 min - 1/2oz amarillo
10 min - 1/2oz citra

5 min - 1/2oz amarillo
5 min - 1/2oz centennial

flameout - 1/2oz amarillo
flameout - 1/2oz citra

dryhop - 1oz centennial, 1oz citra, 1/2oz cascade

Just bottled today, smelled amazing, like a big basket of ripe tropical fruit :rockin:

Well, at first sampling I would have to say it's pretty awesome. Smells like melons and a lot of grapefruit in the taste.

Thanks for all the help everyone! lol